Calcified Curschmann's spirals and microliths in sputum smears from a case of pulmonary alveolar microlithiasis

Abstract

Pulmonary alveolar microlithiasis (PAM) is an uncommon lung disease (up to December 2014 a total of 1022 cases had been described in the literature in 65 countries) 1 characterized by a diffuse filling of the alveolar spaces by circular lamellated structures (they resemble an onion bulb) principally composed of calcium and phosphate (calcospherites or microliths). This is an autosomal recessive disorder caused by mutations in the SLC34A2 gene, 2 which regulates a protein called type IIb sodium-phosphate cotransporter and is located specifically in the type 2 pneumocytes. SLC34A2 gene mutations are thought to impair the activity of the type IIb sodium-phosphate cotransporter, resulting in the accumulation of phosphate in the alveoli and consequently in the formation of microliths. 3 Patients with PAM usually develop a persistent nonproductive cough and dyspnea, especially during physical exertion but often the disease is discovered before symptoms develop, when a thoracic radiological imaging is done for other reasons (the so-called clinical-radiological dissociation). 4 Other symptoms include hemoptysis, chest pain, and asthenia. Chest radiography and computed tomography usually reveal dense extensive bilateral micronodular opacities and microcalcifications, showing the classical pattern of "sandstorm appearance." 5 Both macroscopic and histopathology alterations are fairly characteristic. The gross pathology of lung specimens reveals a pleural surface that may appear soft or firm and exhibits a granular or nodular pattern. Cut sections reveal extensive microcalcifications and a granular appearance of the parenchyma. 6 In tissue sections, normal respiratory lining epithelium with dilated alveolar spaces containing many concentrically laminated calcified concretions is observed. The presence of microliths in the bronchoalveolar lavage (BAL) fluid is also possible. 7 Diffuse interstitial fibrosis may be observed in more severe cases. 8 Nevertheless, although radiological and histopathological studies are quite documented, reports on PAM and sputum examination are rather scanty. 9,10 Although in both reports, the presence of microliths in sputum smears is reported (one case was a patient with tuberculosis), the observation of calcified Curschmann spirals, forming a relative large calculus, is only stated by Tao 9 (therefore, with our work this finding is the second time that is mentioned). Herein, we show the principal findings observed in two samples of sputum from a 56-year-old male patient who had been previously diagnosed with PAM some years ago through a thoracic CT and a transbronchial lung biopsy. At the moment of obtaining the samples, the disease of this patient was stable, his symptomatology principally being cough, dyspnoea, recurrent episodes of haemoptysis, and asthenia. The samples were obtained from spontaneous expectorations and the smears carried out by means of the "pick-up-smear" technique, fixed in ethanol 968, and stained by the Pap method.In Figure 1A, we can observe the presence of some elonga...

Pulmonary alveolar microlithiasis

“…Histology demonstrating the typical lamellar structure of microliths can help to distinguish them from other airway calculi in the differential. Although Curschmann's spirals, associated with asthma and chronic bronchitis, are composed of glycoproteins and are not typically calcified, patients with PAM may develop a bronchial mold with calcifications that have a similar appearance that is distinct from the classic lamellar calcified bodies that are typical of microliths[58,[60][61][62]. Psammoma bodies are concentric calcified laminated structures that form within epithelial cell aggregates or small tissue fragments and are often associated with adenocarcinoma[45,59,[63][64][65].…”